Optical: systems and elements – Lens – With reflecting element
Reexamination Certificate
2003-09-30
2004-11-16
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With reflecting element
C359S708000, C359S712000, C362S327000, C362S329000
Reexamination Certificate
active
06819506
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to lens systems used for flashlights, bicycle or small vehicle lights, hiking lights, search and rescue lights, medical illumination devices, military lighting devices, and other commercial and industrial applications wherein light from a light source is projected through a lens in order to alter characteristics of the projected beam. More particularly, the present invention is directed to an optical lens system which is particularly adapted for use with a high powered light emitting diode (LED) light source having a hemispherical lens associated therewith. The LED source is designed to be cooperatively seated within a cavity in a rear portion of a projecting lens. The projecting lens includes arcuate side walls which are designed to be totally internally reflective to project light through a front face of the lens from the optically aligned LED source such that substantially all light from the LED source passes through the lens body and through the front face of the lens in a lambertion pattern. Preferably, the projected light beam creates a generally central hot spot by directing the light rays at angles between approximately 5° and 30° with respect to a central optical axis of the projecting lens.
The present invention is also directed to lenses which are specifically designed to positively optically aligned and secured when mounted within a lens holder whereby heat dissipation from the LED source is assured so as to maintain LED operating temperatures within critically defined operating ranges.
2. Brief Description of the Related Art
It has been know to use various types of solid lenses to direct light emitted from light sources such that light rays are intensified or altered as they pass through the lenses and are projected forwardly of the lenses. Lens configurations are varied to change the projected light pattern to create different lighting characteristics or different fields of projection.
By way of example, in U.S. Pat. No. 2,469,080 to Rosin et al., a unitary lens is disclosed having a projection face and a rear wall having a central cavity extending therein for purposes of providing a chamber for seating a light source. Light from the source is projected laterally and forwardly through the lens and the lateral light is projected or reflected off the inner surfaces of the lens and through the front face of the lens in a collimated pattern wherein the light rays are substantially parallel to one another. With such a lens, the size of the light beam remains generally constant and is generally uniform in intensity across the full width of the beam such that a spot reflected off a surface close to the lens will appear to have approximately the same size as one reflected off a surface which is much farther from the lens.
In U.S. Pat. No. 2,908,197 to Wells et al., a lens for creating a wide angle distribution of light received from a light source is disclosed. In the lens system described, the front face of the lens is altered to create a different light projection pattern. The lens includes a rear cavity in which a light source is seated such that light is projected forwardly and laterally within the lens with the lateral light being reflected from the side walls of the lens forwardly through the various portions of the front face described and shown in the patent. In this manner, different wide angle light patterns are obtained from the light source.
In many instances, lenses are specifically designed for different types of light sources. By way of example, in U.S. Pat. No. 5,757,557 to Medvedev et al., a beam forming lens is disclosed particularly for use with an incandescent light source such as a conventional incandescent bulb. As with other prior art lenses, the lens body includes a front face, tapering side walls and a rear cavity. The cavity is of a size within which the incandescent light source is cooperatively received. Light from the light source is projected substantially 360° with respect to the incandescent bulb and is reflected by the inner side walls of the lens forwardly through the front face. As taught in the patent, it is desired that the lens reflect as much energy from the incandescent light source as is possible so that light normally projected rearwardly of the incandescent bulb is projected forwardly in a collimated or parallel beam or pattern from the front face of the lens.
In U.S. Pat. No. 6,547,423 to Marshall et al., an LED optical device is disclosed which is particularly designed to use with light emitting diode (LED) modules for purposes of improving the efficiency and performance of the light being projected from the LED source. The lenses disclosed include both generally planar and shaped outer front faces with each lens including tapered side walls. Each lens further includes a cavity which defines a refractive inner side wall and a refractive end wall or lens in which the LED source is seated. Light from the LED source is projected both forwardly and laterally and the lateral light energy is reflected from the inner reflective walls of the lens such that light projected from the front face of the lens is collimated. In some embodiments, the angle of the light may be modified, however, light rays from the lens remain generally parallel.
Other prior references of interest include U.S. Pat. No. 2,215,900 to Bitner et al., U.S. Pat. No. 2,254,961 to Harris, U.S. Pat. No. 5,813,743 to Maka, U.S. Pat. No. 5,485,317 to Perissinotto et al., U.S. Pat. No. 6,527,419 to Galli and U.S. Pat. No. 6,560,038 to Parkyn, Jr. et al.
From the foregoing, the configuration and elements of a lens system for collecting and projecting light from a source is dependent on features of the source. Thus, lenses that may work well with incandescent light sources will not function for other types of lights such as LED light sources due to different focal as well as other physical characteristics of the differing light sources.
New higher power light emitting diodes are being developed. Examples of such newer high powered LEDs are described in U.S. Pat. No. 6,274,924 to Carey et al., the contents of which are incorporated herein in its entirety by reference. Commercially, high powered LEDs are marketed under the names LUXEON I Emitter, LUXEON III Emitter, LUXEON Star and LUXEON V Star.
The new configuration or physical package of the high power LEDs differs from conventional LEDs and also creates additional problems due to the significant amount of heat developed by the high power LEDs.
The thermal requirements for the new high power LEDs is critical. A junction temperature for such high powered LEDs cannot exceed approximately 120° Celsius. High power LEDs can shift to slightly higher wave lengths with a rise in the junction temperature. The human eye is sensitive to color shift and this must also be accounted for in a design of a projection system.
Further, high power LEDs experience a loss of light output as their junction temperature increases. Therefore, the lower the junction temperature maintained, the better the luminous efficiency of the light source. By way of example, if there is exactly enough heat dissipation at an ambient temperature of 10° Celsius with respect to the junction temperature, as the temperature rises, the light from the LED will begin to dim.
High power LEDs also become more unreliable when the junction temperatures exceed the maximum designed. The maximum junction temperatures are based upon the allowable thermal stress of encapsulates which surround components of the LEDs, such as silicone. Further, LEDs may have a reduced life expectancy due to temperatures exceeding maximum design temperatures. Newer high power LEDs may have a life expectancy of 100,000 hours while still maintaining 70% of their original efficiencies. However, if temperatures rise above the maximum junction temperature, the high power LEDs will drop to 70% of their original efficiency immediately without regard to number of hours of operation.
Due to the need to maintain temperat
Kappel David W.
Taylor James R.
Taylor Wilfrid E.
Taylor Wilfrid L.
Wu Paul Nam-Kwan
Dowell & Dowell , P.C.
Epps Georgia
Hasan M.
Infinity Trading Co. Ltd.
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